Magnetic recording media such as high density rigid disks, ultra high density floppy disks, digital audio tapes and video tapes can be read by a magnetic recording head as the recording media moves past the recording head. The recording head is in very close proximity to the recording media and frequently contacts the recording media. Such contact causes wear of the thin layer of magnetic material on the recording media and shortens the useful life of the recording media. Older technology media types such as standard audio, VHS video and standard floppy disks experience wear problems due to unsuitable lubricants. These problems included increased friction, scratching and adhesion. Such problems are addressed by the new, more efficient internal and boundary lubricant systems of the present invention. The lubricant of the present invention is designed to be used with the more advanced forms of magnetic recording media mentioned above.
Another important characteristic of a phosphazene lubricant for magnetic media is solvent compatibility of the lubricant. The lubricant must be dissolvable in solvents such as tetrahydrofuran and acetone. The lubricant must also be stable in the presence of water and base.
Lubricants for magnetic media are known in the art, but such lubricants are limited to those for more mature counter-parts of the magnetic media such as standard audio, VHS video and standard floppy disks. Furthermore, these lubricants do not demonstrate solvent compatibility with a wide range of organic solvents and are not stable in water and base. Examples of such lubricants are described in U.S. Pat. No. 4,613,548 to Lum, issued on Sep. 23, 1986, which discloses a magnetic recording media containing a normally liquid phosphazene lubricant, e.g. low molecular weight linear or cyclic polyfluoroalkoxy phosphazene mixtures. Such fluoroalkoxy substituted phosphazenes as recited in the Lum reference do not exhibit the stability of the present invention in bases and water.
U.S. Pat. No. 4,029,634 to Meredith discloses a flame retardant composition for a polymer including a halogen substituted hexakis-(substituted phenoxy) cyclotriphosphazene in the polymer. The halogenated phenoxy substituent utilizes either bromine or chlorine.
U.S. Pat. No. 4,601,843 to Carr et al. discloses a cyclic phosphazene based functional fluid which exhibits fire resistance, fluidity and compatibility with engine seal compositions. The phosphazene is substituted with at least one alkoxy moiety and three different moieties which may include a fluorinated phenoxy moiety or a fluoroalkylphenoxy moiety among various other compounds.
U.S. Pat. No. 3,291,865 to Kuber et al. discloses cyclic polymeric phosphonitrilate compositions substituted with a first substituent which is a polyfluoroalkoxy compound and a second substituent which may include a halogenated lower alkyl-substituted phenoxy or a halogen substituted phenoxy.
U.S. Pat. No. 3,316,330 to Nichols, discloses a polymeric phosphonitrile substituted with a meta-trifluoromethoxyphenoxy substituent and a phenoxy substituent. The composition is useful as a working fluid, a high temperature lubricant and a plasticizer.
It is a primary object of the present invention to provide a solvent compatible, magnetic recording media lubricant, including a cyclic phosphazene completely substituted with fluorinated phenoxy moieties. An additional object of the invention is to provide a lubricant which is stable in bases and water and at high temperatures.
Yet another object of the present invention is to provide high density, state of the art recording media, such as high density rigid disks, ultra high density floppy disks, digital audio tape, 8 mm video tape and super VHS tape including a lubricant which may be used as an internal or boundary lubricant system to minimize wear and improve overall performance.